transport: Set the correct properties for other H264 encoders than OpenH264

x264enc and vtenc_h264 take the bitrate property in kbit/s instead of
bit/s, and x264enc should be set to zero-latency mode for realtime
communication.
transport: Remove unused capsfilter element

This is not added to the pipeline or used in any other way.
transport: Remove capsfilter after depayloader and add parser before videorepair

The capsfilter would cause stream format conversion twice in the worst case,
and in the best case have no effect at all. However adding a parser in front
of videorepair is a good idea so that we're guaranteed to have keyframes
marked correctly.
transport: Add a capsfilter after the encoder

And repurpose the now unused _owr_payload_create_encoded_caps() to
get the caps for it.

Here we now tell the encoder to create streams with a specific
profile or level. Currently this is only done for H264 to enforce
baseline profile, as anything else might not be supported by decoders.
transport: Disable passthrough mode in h264parse

Currently the detection if we actually can do passthrough or not
is broken in h264parse. It would go into passthrough mode in some
cases where we would really need h264parse to extract information
from the bitstream for us.